WO2007069612A1

WO2007069612A1 - Optical head and optical information device

Info

Publication number: WO2007069612A1
Application number: PCT/JP2006/324778
Authority: WO
Inventors: Yoshiaki Komma; Kanji Wakabayashi; Kousei Sano; Toshiyasu Tanaka; Keiichi Matsuzaki; Hidenori Wada
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2005-12-14
Filing date: 2006-12-12
Publication date: 2007-06-21
Also published as: US20090310465A1; JPWO2007069612A1; US8144564B2

Abstract

An optical head is provided with a first light source for radiating light having a first wavelength; a beam splitter for splitting the light radiated from the first light source into a first luminous flux and a second luminous flux traveling in a first direction and a second direction different from the first direction, respectively; a first collimating lens for converting exitance of the first luminous flux; a first mirror for changing the traveling direction of the first luminous flux, the exitance of which is converted; a first objective lens for converging the first luminous flux, the traveling direction of which is changed, on a recording plane of a first optical disc; a movable body for holding the first objective lens; a first light detector which receives the first luminous flux reflected on the recording plane of the first optical disc and converts it into electric signals; a light collecting lens for collecting the second luminous flux; and a second light detector which receives the second luminous flux collected by the light collecting lens and converts it into electric signals.

Description

Optical head and optical information device

Technical field

The present invention relates to an optical information apparatus that optically records and reproduces information and an optical head used in the optical information apparatus. The present invention also relates to an application device equipped with an optical information device. Background art

[0002] Optical discs are widely used as information recording media capable of recording large-capacity information, and optical discs with higher recording density have been developed as technology advances.

[0003] The first popularized optical disc was the compact disc (CD), and then the digital versatile disc (DVD) became popular. A DVD can record information at a recording density about 6 times that of a CD, and can record a large amount of data on a single DVD. For this reason, it is used especially for recording video information with a large amount of information. In recent years, next-generation optical discs capable of recording information at higher recording densities, such as Blu-ray Disc (BD) and HD-DVD, have been developed, and in particular, they have begun to be used for recording high-definition video. I am.

[0004] In order to increase the recording density of an optical disc and realize a large capacity, it is necessary to make the light spot of an optical beam used for recording and reproduction smaller. This is achieved by shortening the wavelength of the laser beam used as the light source and increasing the numerical aperture (NA) of the objective lens for forming the light spot. For example, DVD uses a light source with a wavelength of 660 nm and an objective lens with a numerical aperture (NA) of 0.6. In addition, for example, by using a blue laser with a wavelength of 405 nm and an objective lens of NAO.85, a next-generation optical disc capable of realizing a recording density five times the recording density of the current DVD will be realized.

[0005] As various optical discs are developed, compatibility of optical disc apparatuses becomes important. In consideration of the convenience of the user, it is preferable that the optical disc apparatus supports a plurality of optical discs. Specifically, it is preferable that the optical disc apparatus corresponding to the next generation optical disc can record and reproduce a CD or a DVD. In this case, the numerical aperture of the objective lens While it is difficult to increase the working distance to be as high as 85, as with an objective lens for DVD or CD, an optical information device capable of recording / reproducing next-generation optical discs has the objective for next-generation optical discs. It would be desirable to have a lens and at least one objective lens used to record and playback CDs or DVDs.

[0006] The objective lens is driven in the focusing direction and the tracking direction by an objective lens actuator configured by a magnetic circuit or the like. As a result, the objective lens is controlled so as to maintain a predetermined interval of the optical disk force in the focus direction, and is controlled so as to follow the center of the track in the tracking direction.

[0007] For this reason, in an optical information device corresponding to a plurality of optical discs having different recording densities, a plurality of objective lenses must be mounted on the movable portion and configured to be movable in the focusing direction and the tracking direction. Patent Document 1 shows an example of such an optical information device. As shown in FIG. 12, in the optical information device of Patent Document 1, the light beam 61 radiated also by the first light source (not shown) is converted into approximately parallel light by the collimating lens 62, and is formed into a flat plate-like rising mirror. 63, the optical axis is bent so as to be perpendicularly incident on the optical disk 65 having a high recording density. The first objective lens 65 converges the light beam 61 on the recording surface of the optical disk 65.

[0008] In addition, the light beam 66 radiated by the second light source (not shown) force is converted into approximately parallel light by a collimator lens 67, and an optical disk 70 whose optical axis is low in recording density by a flat rising mirror 68. It is bent so that it may enter perpendicularly to. The second objective lens 69 causes the light beam 66 to converge on the recording surface of the optical disc 70.

The objective lens actuator 71 moves the first objective lens 64 fixed to a movable part (not shown) in the focusing direction F perpendicular to the recording surface of the optical disk 65 having a high recording density and the tracking direction T of the optical disk 65. It can be moved in both directions. Similarly, the objective lens actuator 72 moves the second objective lens 69 fixed to a movable part (not shown) to the focusing direction F and the optical disk 70 that are orthogonal to the recording surface of the optical disk 70 having a low recording density. It can be moved in both directions T. As described above, in the optical information device disclosed in Patent Document 1, the two objective lenses are driven by different objective lens actuators. [0010] Patent Document 2 discloses an optical information device in which two objective lenses are supported on the same movable part and driven in a focusing direction and a tracking direction by one objective lens actuator.

Patent Document 3 discloses another example of an optical information device in which two objective lenses are supported on the same movable part and driven in a focusing direction and a tracking direction by one objective lens actuator. The optical information device shown in FIG. 13 is compatible with three optical discs having different recording densities, and includes three light sources. Specifically, a semiconductor laser 73, a DVD module 85 in which a semiconductor laser is incorporated, and a CD module 83 are provided.

The semiconductor laser 73 emits a laser beam of 408 nm and is used when information is recorded / reproduced on / from a high-density optical disk. The light beam emitted from the semiconductor laser 73 passes through the collimator 74 and enters the half mirror 75. Part of the light incident on the half mirror 75 is incident on the monitor photodiode 78 and most of the light is incident on the rising mirror 88. The rising mirror 88 reflects light toward the objective lens 80. The light reflected by the optical disk follows the reverse path, enters the half mirror 75, passes through the cylindrical lens 77, and then enters the photodetector 76.

[0013] The DVD module 85 includes a red semiconductor laser that emits a laser beam of 658 nm and a photodetector, and is used when information is recorded on and reproduced from a DVD. The light emitted from the semiconductor laser of the DVD module 85 passes through the DVD collimator 86 and the polarization beam splitter 87 and enters the rising mirror 88. The rising mirror 88 reflects light toward the objective lens 81. The light reflected by the optical disc follows the reverse path and enters the photodetector of the DVD module 85.

[0014] The CD module 83 includes an infrared semiconductor laser that emits a laser beam of 785 nm and an optical detector, and is used when information is recorded on and reproduced from a CD. The light emitted from the semiconductor laser of the CD module 83 passes through the CD collimator 84 and the polarization beam splitter 87 and enters the rising mirror 88. The raising mirror 88 reflects light toward the objective lens 81. The light reflected on the optical disk follows the reverse path and enters the photodetector of the CD module 83. The objective lenses 80 and 81 can be supported by a holding member 79 constituting a movable body, and the holding member 79 is supported by a wire 82 so as to be movable in the focusing direction and the tracking direction.

Patent Document 1: JP 2002-208173 A

Patent Document 2: Japanese Patent Application Laid-Open No. 11-120587

Patent Document 3: Japanese Patent Laid-Open No. 2005-293686

Disclosure of the invention

Problems to be solved by the invention

However, since the optical information device of Patent Document 1 includes two objective lens actuators, the distance between the objective lens 64 and the objective lens 69 cannot be reduced, and the optical head of the optical information device can be reduced. It is difficult to downsize. In order to avoid this problem, if the objective lens actuators 71 and 72 are made small, there is not enough space to attach a coil or magnet to obtain a driving force on the movable part side, and the driving force cannot be obtained sufficiently. was there.

[0017] In the optical information device of Patent Document 2, the optical axis incident on one of the two objective lenses extends from the light source to the objective lens in a straight line. For this reason, there has been a problem that the thickness of the optical head in the direction perpendicular to the optical disk surface becomes extremely large.

[0018] Patent Document 3 discloses an optical head that can be made thin by launching light emitted from a plurality of light sources using a prism. However, in particular, the arrangement of components in the horizontal direction is not taken into consideration, and when the optical head tries to access the innermost circumference of the optical disk, there arises a problem that the spindle motor and the optical head interfere with each other.

[0019] A blue semiconductor laser is used for recording and reproduction of an optical disc having a high recording density such as BD and HD-DVD. Blue semiconductor lasers have a higher drive voltage and higher power consumption than light sources used for recording and playback such as DVDs and CDs. According to the study of the present inventor, when the optical head is downsized, the heat generated by the blue semiconductor laser deteriorates the signal Z noise ratio of the optical detector in the optical head, making stable recording and reproduction difficult. There was a problem of becoming a problem.

[0020] Also, when recording on an optical disc with high recording density, it is necessary to accurately form recording marks and pits on the information recording surface of the optical disc. For this reason, the light emitted from the light source The amount needs to be monitored. In particular, as the recording density increases, the recording marks and pits also become smaller. Therefore, it is necessary to monitor the amount of light emitted from the light source at a higher signal Z noise ratio and at a higher frequency. Patent Documents 1 to 3 do not disclose a method for monitoring an appropriate amount of light in order to perform recording / reproduction on an optical disc having a high recording density, such as BD and HD-DVD.

[0021] When the light is converged by a high NA objective lens and recording / reproducing is performed on a high-density optical disc, the distance from the light incident surface of the optical disc to the information recording surface of the optical disc, that is, the base material The wavefront is greatly disturbed by the thickness error. This disturbance is called spherical aberration. Spherical aberration is almost proportional to the fourth power of NA. Therefore, when using an objective lens with a high NA, correction means using spherical aberration is necessary. Patent Documents 1 to 3 do not disclose a specific configuration for efficiently correcting spherical aberration with the minimum number of parts in the optical system of the prior art.

[0022] The present invention solves at least one of the problems of the prior art as described above, and includes at least one light source for high recording density, and is compatible with a plurality of types of optical discs that are small and excellent in stability. The object is to provide a head.

Means for solving the problem

[0023] The optical head of the present invention includes a first light source that emits light of a first wavelength, and a first light that travels in a second direction different from the first direction and the light emitted from the first light source. A beam splitter that branches into a first light beam and a second light beam, a first collimating lens that converts a divergence degree of the first light beam, and a first direction lens that changes a traveling direction of the first light beam converted in the divergence degree. 1 a mirror, a first objective lens for converging the first luminous flux whose traveling direction has changed toward the recording surface of the first optical disc, a movable body for holding the first objective lens, and the first optical dice. Receiving the first light beam reflected on the recording surface of the disk and converting it into an electrical signal; a condensing lens for condensing the second light beam; and a second light beam condensed by the condensing lens And a second photodetector that converts it into an electrical signal That.

Preferably, according to an embodiment, the optical head further includes a second mirror that changes a traveling direction of the second light beam emitted from the beam splitter, and the second mirror is arranged in the second direction. To change the traveling direction of the traveling light flux in a direction perpendicular to the second direction Arranged relative to the beam splitter.

In a preferred embodiment, the optical axis of the second light beam whose traveling direction is changed by the second mirror and the optical axis of the first light beam whose traveling direction is changed by the first mirror are mutually different. Parallel.

In a preferred embodiment, the second photodetector has an outer shape having a longitudinal direction, and the second detection is performed so that the longitudinal direction is substantially parallel to the optical axis of the first collimating lens. A vessel is placed.

In one preferred embodiment, the second detector has an electrical connection terminal on a side surface located in the longitudinal direction.

[0028] In a preferred embodiment, the optical head further comprises a driving device for moving the position of the first collimating lens in a direction parallel to the optical axis of the first collimating lens, and the driving device includes: The first optical disc is disposed on the outer peripheral side with respect to the optical axis of the first collimating lens.

[0029] In one preferred embodiment, the optical head further includes a concave lens and a diffractive lens formed on the curved surface of the concave lens, and further includes a lens that corrects chromatic aberration of the first objective lens.

[0030] In a preferred embodiment, the first light source and the first photodetector are arranged on opposite sides with respect to the optical axis of the first collimating lens.

[0031] In a preferred embodiment, the optical head includes a second light source that emits light having a second wavelength longer than the first wavelength, and a second mirror that changes a traveling direction of the light emitted from the second light source force. And a second objective lens that converges the light of the second light source whose traveling direction has been changed by the second mirror toward the recording surface of the second optical disk, and the second objective lens is supported by the movable body Has been.

[0032] In a preferred embodiment, the first light source and the second light source are arranged on the outer peripheral side of the first optical disc with respect to the optical axis of the first collimating lens.

[0033] In one preferred embodiment, the optical head further includes a drive circuit for driving the first light source and the second light source, and the drive circuit includes the first light source and the second light source. 2 Close to the light source. [0034] In a preferred embodiment, the second wavelength is a wavelength used for DVD recording / reproduction, and the first wavelength is a wavelength used for recording / reproduction of an optical disc having a higher density than the DVD.

In one preferred embodiment, the first objective lens and the second objective lens are arranged along a tangential direction of the first optical disc and the second optical disc.

[0036] In a preferred embodiment, the first objective lens is located on a straight line passing through the center of the first optical disc and parallel to the moving direction of the seek operation of the optical head.

[0037] In a preferred embodiment, the second objective lens has an edge with a width of 0.16 mm or more and 1 mm or less.

[0038] In a preferred embodiment, the surface of the edge of the objective lens is mirror-finished.

The optical information device of the present invention is obtained from the optical head defined in any one of the above, a spindle motor that rotationally drives the first optical disk, and at least the first photodetector of the optical head. And an electric circuit for controlling the optical head based on the signal.

[0040] A computer of the present invention includes the optical information device.

[0041] An optical disc player of the present invention includes the optical information device.

[0042] An optical disc recorder of the present invention includes the optical information device.

[0043] An optical disk server of the present invention includes the optical information device.

The invention's effect

[0044] According to the present invention, by providing the condensing lens, it is possible to collect light incident on the second photodetector and reduce the amount of light in a small area of the light detection region. This makes it possible to measure the amount of light emitted from the first light source in a high frequency band and with a high signal Z-noise ratio. Therefore, it is possible to realize an optical head that can keep the emission intensity of the first light source constant and can obtain a high-quality reproduction signal with little jitter.

[0045] Further, according to the present invention, it is possible to reproduce or record an optical disk using an objective lens having a high numerical aperture up to the inner circumference side. In addition, the temperature rise of the light source can be suppressed and recording / reproduction can be performed stably. In addition, information can be recorded at high speed on each of a plurality of optical discs having different recording densities. [0046] Furthermore, since the optical component can be stored in a limited space, the optical head can reach the innermost circumference of the optical disk recording section, and data can be recorded or reproduced.

[0047] Therefore, an optical head in which a plurality of objective lenses for realizing an optical information apparatus capable of recording and reproducing with respect to a plurality of optical discs having different recording densities is mounted on a movable portion is realized.

Brief Description of Drawings

FIG. 1 is a perspective view mainly illustrating a configuration of an optical system in an embodiment of an optical head according to the present invention.

FIG. 2 is a schematic diagram partially showing FIG. 1 in a plan view and a side view.

FIG. 3 is a plan view of an embodiment of an optical head.

FIG. 4 is a side view showing an optical system of light incident on a second photodetector.

FIG. 5 is a side view showing the structure of a chromatic aberration correcting lens used in the first embodiment.

FIG. 6 is a cross-sectional view showing the structure of a second objective lens.

FIG. 7 is a diagram showing a configuration of an embodiment of an optical information device.

FIG. 8 is a diagram illustrating a configuration of an embodiment of a computer.

FIG. 9 is a diagram showing a configuration of an embodiment of an optical disc player.

FIG. 10 is a diagram showing a configuration of an embodiment of an optical disc recorder.

FIG. 11 is a diagram showing a configuration of an embodiment of an optical disk server.

FIG. 12 is a side view showing the structure of a conventional optical head.

FIG. 13 is a perspective view showing the structure of another conventional optical head.

Explanation of symbols

[0049] 31 First light source

56, 57, 58 Luminous flux

33 1st collimating lens

39 Second collimating lens

60 prism

60a, b slope

35 First optical disc 46 3rd optical disc

34 First objective

41 Second objective lens

59 Polarizing beam splitter

36 First photodetector

37a Second light source

40 polarization hologram

37, 43 Integrated unit

43a Third light source

43b hologram

45 Objective lens actuator

320 2nd optical disc

BEST MODE FOR CARRYING OUT THE INVENTION

[0050] (First embodiment)

Hereinafter, embodiments of the optical head according to the present invention will be described.

FIG. 1 is a perspective view mainly illustrating the configuration of an optical system of an optical head according to the present invention, and FIG. 2 is a schematic diagram partially showing FIG. 1 in a plan view and a side view. 3 is a plan view of FIG. In these figures, T is the tracking direction and F is the focusing direction. Y is a direction perpendicular to the tracking direction. In other words, Y is the direction in which the pit row or track groove extends.

[0052] In FIG. 2, the side of the optical head sandwiched between two wavy lines W and W is a side view, that is,

1 2

The structure in a plane parallel to direction F and direction Y is shown, with two wavy lines W and W

1 2 On the outside, the plan view, ie the structure in the plane parallel to direction T and direction Y, is shown.

The optical head can perform at least one of recording and reproduction with respect to the first optical disc 320 having a high recording density such as BD, HD-DVD and the like.

[0054] In order to perform at least one of recording and reproduction with respect to the first optical disc 35, the optical head includes a first light source 31, a beam splitter 32, a first collimating lens 33, a first mirror 60a, and a first mirror 60a. And a first photodetector 36.

The first light source 31 is configured by a semiconductor conductor laser or the like, and emits light having a first wavelength, for example, blue light. The light 56 emitted from the first light source 31 is branched by the beam splitter 32 into a first light beam 56 ′ ′ and a second light beam 56 ′. The second light flux is detected by the photodetector 2 in order to control the intensity of the light emitted from the first light source 31, as will be described in detail below.

The first light beam enters the first collimating lens 33, and the first collimating lens 33 converts the divergence of the first light flux. The first light flux whose divergence has been converted enters the inclined surface 60a of the prism 60 that functions as the first mirror. The slope 60a changes the traveling direction of the first light flux. Specifically, as shown in FIGS. 1, 2 and 3, the first light flux traveling in the plane parallel to the first optical disk 35 is directed to the first optical disk 35 by about 90 degrees, and the traveling direction is changed. It is changed and made incident on the first objective lens 34.

The first objective lens 34 converges the first light beam toward the recording surface of the first optical disc 35. The first light beam reflected on the recording surface of the first optical disk 35 follows the original optical path in the reverse direction and is branched by the beam splitter 32 in a direction different from that of the first light source 31.

[0058] The first photodetector 36 receives the first light flux and performs electrical conversion to obtain an information signal and a servo signal (a focus error signal for focusing control and a tracking signal for tracking control). Convert to signal.

The optical head is preferably capable of performing at least one of recording and reproduction on the second optical disk 320 having a different recording density in addition to the first optical disk 35. In the present embodiment, the second optical disk 320 is, for example, a DVD. For this purpose, the optical head includes an integrated unit 37, a second collimating lens 39, and a second objective lens 41.

[0060] The integrated unit 37 includes a second light source 37a that emits light of a second wavelength (for example, red light) having a wavelength longer than the first wavelength, and a photodetector (not shown). The light 57 emitted from the second light source 37a is guided to the second collimating lens 39 by the dichroic mirror 38. The second collimating lens 39 converts the divergence of the light emitted from the second light source.

The light 57 whose divergence has been converted enters the inclined surface 60b of the prism 60. The slope 60b changes the traveling direction of the light 57. Specifically, as shown in FIGS. 1, 2 and 3, the second optical disk The traveling direction of the light 57 traveling in the plane parallel to 320 is changed to about 90 degrees so as to be directed to the second optical disk 320, and is incident on the second objective lens 41.

The second objective lens 41 converges the light 57 toward the recording surface of the second optical disk 320. The light 57 reflected on the recording surface of the second optical disk 320 follows the original optical path in the opposite direction, is branched in a direction different from the initial direction by a branching means such as a polarization hologram 40, and enters the photodetector 54. The photodetector 54 receives the reflected light and converts it into an electrical signal for obtaining an information signal and a servo signal (a focus error signal for focusing control and a tracking signal for tracking control) by photoelectric conversion. . For example, by incorporating the photodetector in the integrated unit 37 of the light source and the photodetector, the photodetector can be made smaller and thinner, and stability can be obtained.

[0063] More preferably, the optical head can perform at least one of recording and reproduction on the third optical disk 46 having a different recording density in addition to the first optical disk 35 and the second optical disk 320. . In the present embodiment, the third optical disk 46 is a CD, for example. For this purpose, the optical head comprises an integrated unit 43 and a photodetector 54.

[0064] The integrated unit 43 includes a third light source 43a that emits light with a third wavelength longer than the second wavelength (for example, infrared light). The light 58 emitted from the third light source 43 a passes through the dichroic mirror 38 and enters the second collimating lens 39. A relay lens 44 may be provided between the integrated unit 43 and the diced opening mirror 38. The light 58 whose divergence has been converted by the second collimating lens 39 enters the inclined surface 60b of the prism 60, and the traveling direction is converted. As a result, the traveling direction of the light 58 traveling in the plane parallel to the third optical disk 46 is changed by about 90 degrees toward the third optical disk 46 and is incident on the second objective lens 41.

[0065] The light 58 reflected on the recording surface of the light 46 follows the original optical path in the reverse direction, and is branched in a direction different from the first by a branching means such as the hologram 43b, so that the light detection in the integrated unit 43 is performed. Incident light. The photodetector receives the reflected light and photoelectrically converts it into an electrical signal for obtaining an information signal and a servo signal (a focus error signal for focusing control and a tracking signal for tracking control). By incorporating the photodetector in the integrated unit 37 together with the light source, for example, the optical head can be reduced in size and thickness, and stability can be obtained. [0066] In the present embodiment, the cross section of the rising prism 60 is a triangle, and the two mirrors can be configured by two independent members having the slopes 60a and 60b that function as two mirrors. Good. Further, the apex of the rising prism 60 (ridge line when viewed as a whole prism) may be chamfered to prevent chipping.

[0067] In the present embodiment, the second light source 37a and the third light source 43a are configured as separate components. Therefore, by using the dichroic mirror 38, light beams emitted from both light sources are used. We are trying to increase usage efficiency. However, the second light source 37a and the third light source 43a may be integrated on a single semiconductor chip. In this case, the dichroic mirror 38 can be omitted.

[0068] The optical head of the present invention has a small outer shape, and has various structural features in order to exhibit stable and excellent optical characteristics. Hereinafter, features of the optical head according to the present invention will be described in order. Hereinafter, when the first optical disc 35, the second optical disc 320, and the third optical disc 46 are collectively referred to, they may be simply referred to as optical discs. Similarly, the first objective lens 34 and the second objective lens 41 may be collectively referred to simply as an objective lens.

First, characteristics of the optical system for high recording density in the optical head of the present invention will be described. When recording / playback on high-density optical disks such as BD and HD-DVD, it is necessary to use a light source with a short wavelength. In the present embodiment, the first light source 31 emits blue light, and is used to record information on a high recording density optical disk or to reproduce information from a high recording density optical disk. In order to stably record information by the first light source 31, an area where pits or marks are formed (recording pit part) and an area where no pits or marks are formed (non-recording part or erasure part) Therefore, it is necessary to keep the emission intensity of the first light source 31 constant.

For this purpose, as shown in FIG. 1, the optical head of the present embodiment includes a photodetector 2 that measures the emission intensity of the first light source 31. In addition, in order to guide the light to the photodetector 2, the beam splitter 32 includes a first light flux that travels the light 56 emitted from the first light source 31 in a second direction different from the first direction and the first direction, respectively. Branches to 56 '' and the second luminous flux 56 '. The first beam enters the collimating lens 33 described above. The second light beam 56 ′ enters the photodetector 2.

[0071] The second light flux 56 'is in a divergent state, like the first light flux 56''. For this reason, electrical noise In order to obtain a higher signal, the area of the light receiving portion of the photodetector 2 needs to be increased. On the other hand, in order to obtain a signal in a high frequency band, it is preferable to reduce the area of the light receiving portion and to reduce the electric capacitance (capacitance) of the light receiving portion. Thus, there is a trade-off between improving the signal Z-noise ratio (SZN ratio) and increasing the frequency band, and it is difficult to achieve both.

In order to solve this problem, the optical head of the present embodiment includes a condenser lens 1 that condenses the second light beam 56 ′ branched by the beam splitter 32, as shown in FIGS. . The condensing lens 1 may convert the divergent second light beam 56 ′ into a condensing state. In FIG. 4, the second light flux 56 ′ does not necessarily have to be focused on the force disposed with respect to the photodetector 2 so as to form a focal point in the photodetector 2. The second light beam 56 ′ emitted from the beam splitter 32 should be condensed so as to be condensed!

[0073] By providing the condensing lens 1 in this way, it is possible to collect light incident on the photodetector 2 and collect a large amount of light in a small area of the light detection region. As a result, the amount of light emitted from the first light source 31 can be measured in a high frequency band and with a high signal Z noise ratio.

[0074] Preferably, the optical head includes a smooth mirror (second mirror) 3, and changes the traveling direction of the second light beam 56 'emitted from the beam splitter 32. More specifically, the mirror 3 is disposed with respect to the beam splitter 32 so that the traveling direction of the second light beam 56 ′ emitted from the beam splitter 32 changes substantially at a right angle. Thus, as shown in FIGS. 1 and 4, when the light emitted from the first light source 31 is arranged so as to travel in the T direction, the mirror 3 causes the optical axis of the second light beam 56 ′ and the slope of the prism 60 to The optical axes of the first light fluxes 56 6 ′ whose traveling directions are changed by 60 a are parallel to each other. As a result, the photodetector 2 can be arranged in the F direction, not in the T direction, with respect to the optical path of the light 56 emitted from the first light source 31. Therefore, it is possible to prevent the components constituting the optical head from spreading in the T direction, and the optical head and the spindle motor that rotates the optical disc when the optical head moves toward the inner periphery of the optical disc. Interference can be prevented.

In the present embodiment, the force by which the traveling direction of the second light beam 56 ′ is changed by the mirror 3 so that the second light beam 56 ′ travels toward the first objective lens 34 side. Go to the other side Change the direction of travel as you go.

[0076] Furthermore, when the photodetector 2 has a rectangular parallelepiped shape having a longitudinal direction, the longitudinal direction is approximately parallel to the optical axis of the first collimating lens ₃₃ , that is, the longitudinal direction is parallel to the Y direction. It is preferable to arrange the photodetector 2 so that Furthermore, it is preferable that the electrical terminal of the photodetector 2 is provided on a side surface located in the longitudinal direction. As a result, the components can be arranged in the optical head without the light detector 36 and the light detector 2 interfering with each other. In addition, it is possible to suppress the components that make up the optical head from spreading in the T direction. Therefore, recording and reproduction can be performed by bringing the optical head closer to the inner circumference side of the optical disk.

Next, the first collimating lens 33 will be described. The first objective lens 34 used for recording reproduction of a high recording density optical disc has a numerical aperture (NA) of 0.85 or higher. Due to the large numerical aperture, when recording or playback is performed on the first optical disk 35, spherical aberration is noticeably generated due to the difference in the thickness of the transparent substrate covering the surface of the information recording surface of the first optical disk 35. To do.

In this embodiment, by moving the first collimating lens 33 in the optical axis direction of the first collimating lens 33, the divergence and convergence degree of the directional light from the first collimating lens 33 to the first objective lens 34 is achieved. To change. Since the spherical aberration changes when the divergence / convergence of the light incident on the first objective lens 34 changes, this is used to correct the spherical aberration due to the difference in thickness of the base material.

For this purpose, the optical head includes a driving device 8. The drive device 8 can be constituted by, for example, a stepping motor, a brushless motor, or the like and a known mechanical element that converts a rotational driving force into a translational driving force.

The holder that holds the first collimating lens 33 may be formed integrally with the collimating lens 33 in order to reduce the number of parts. The first collimating lens 33 is converted so as to loosen the parallelism, that is, to reduce the divergence. The first collimating lens 33 may be composed of a combination of a concave lens and a convex lens. In this case, spherical aberration can be corrected even if either the concave lens or the convex lens is moved in the direction parallel to the optical axis by the driving device 8.

[0081] Here, the first objective lens 34 can be moved to the inner circumference side of the optical disk (radius of about 20mm). In order to achieve this, it is preferable that the optical head does not protrude from the first objective lens 34 as much as possible to the spindle motor 7 side. For this reason, as shown in FIG. 3, the driving device 8 is located on the opposite side of the spindle motor 7 from the optical axis 33a of the first collimating lens 33 in the plane parallel to the first optical disk 35, that is, As indicated by the arrow 33A, it is preferably arranged on the outer peripheral side of the first optical disc 35. As a result, it is possible to avoid the interference between the driving device 8 of the first collimating lens 33 and the spindle motor 7, and to move the optical head to the inner peripheral side of the optical disk.

As shown in FIGS. 1 to 3, it is preferable to arrange a collimating lens 33 which is a spherical aberration correcting means between the beam splitter 32 and the objective lens 34. As described above, the collimating lens 33 is moved along the optical axis direction by the power of the driving device 8 to change the divergence and convergence of the light incident on the first objective lens 34, thereby changing the spherical surface. Aberration can be controlled.

As shown in FIG. 13, Patent Document 4 discloses disposing a collimating lens 74 between a light source 73 and a beam splitter 75. In this case, even if the collimating lens 74 is moved to correct the spherical aberration, the light reflected by the optical disk and incident on the photodetector 76 does not pass through the collimating lens 74. And the image formation relationship between the optical disc and the photodetector is different. As a result, an accurate focus error signal cannot be detected by the photodetector 76.

On the other hand, according to the present invention, the collimating lens is located between the light source and the optical disc and between the optical disc and the photodetector, so that the imaging relationship between them is maintained. Therefore, spherical aberration can be performed without changing the light convergence state in focus control, and a remarkable effect that both focus control and spherical aberration control can be achieved is obtained.

Next, correction of chromatic aberration will be described. When the optical head is mounted on an optical information device that performs both recording and reproduction, the first light source 31 needs to emit light with a larger output than the output during reproduction. In this case, the wavelength of light emitted from the first light source 31 may vary depending on the output. For this reason, the optical head further includes a lens 49 for correcting chromatic aberration in order to correct chromatic aberration due to a change in wavelength of light emitted from the first light source 31. . The lens 49 can be provided between the first objective lens 34 and the prism 60, for example.

As shown in FIG. 5, the lens 49 includes, for example, a concave lens 49a and a diffractive lens 49b having the function of a convex lens. Preferably, the diffractive lens 49b is provided on the curved surface 49c of the concave lens 49a. By providing the diffractive lens 49b on the curved surface 49c having the curvature of the concave lens 49a, when the 0th-order diffracted light reflected on the surface, that is, the light not subjected to the action of the diffractive lens is generated, it is reflected on the plane. Has the effect of preventing the generation of stray light

The optical head may include the lens 55 and the 1Z4 wavelength plate 48. The lens 55 is provided in the vicinity of the first light source 31, has a convex cylindrical surface on the side close to the first light source 31, and has a concave cylindrical surface on the opposite side. As a result, the intensity distribution of the far-field image in two orthogonal directions in the plane perpendicular to the optical axis of the light emitted from the first light source 31 is not equal, that is, the far-field image of the emitted light beam is elliptical. In this case, it is possible to increase the efficiency of light utilization by making the far-field image closer to a circle. Further, the 1Z4 wavelength can improve the light utilization efficiency in the polarization beam splitter 59. Furthermore, by providing the diffraction element 51 and the non-rotationally symmetric lens 50, a servo signal suitable for control can be obtained from the first photodetector 36.

Next, the arrangement of components in the optical head will be described. First, the arrangement of the first light source 31 and the first photodetector 36 in the optical head will be described. The first light source 31 has a driving voltage of about 5V or more. Compared to the drive voltage of the conventional light source for CDs and DVDs, which is about 3V, the first light source 31 needs to be driven at a higher voltage, which increases power consumption and the amount of heat generated from the first light source 31 Also become big. Therefore, it is necessary to fully consider the effects of heat generation.

On the other hand, the first photodetector 36 receives the light reflected from the first optical disk and converts it into an electrical signal. In order to increase the ratio of the signal Z noise by amplifying the signal before the electrical noise is applied to the signal, the first photodetector 36 further includes an amplifier for signal amplification. Are preferably constituted by the same chip. However, since the amplifier also generates heat when energized, if the first photodetector 36 is placed close to the first light source 31, the temperature of the first light source 31 rises due to the heat generated by the amplifier of the first photodetector 36, and the first light source 31 increases. 1 light source 31 It is also conceivable that the wavelength of the light emitted from the first light source 31 is shifted or the life of the first light source 31 is shortened.

Therefore, as shown in FIGS. 1 and 3, the first photodetector 36 and the first light source 31 are in relation to the optical axis of the first collimating lens 33 in a plane parallel to the first optical disk 35. It is preferable to arrange them on opposite sides. As a result, the distance between the first photodetector 36 and the first light source 31 can be increased and the influence of each other's heat can be suppressed. Therefore, an amplifier is integrated in the first photodetector 36 and a high signal is obtained. Obtains Z-noise ratio and prevents temperature rise of the first light source 31

As shown in FIG. 3, the first photodetector 36 preferably has an inner peripheral side of the optical disc or a spindle motor as shown by an arrow 33B with respect to the optical axis of the first collimating lens 33. Located on the side. As apparent from FIG. 3, since the spindle motor 7 is located in the vicinity of the first objective lens 34, the arrow 33B indicates the optical axis of the first collimating lens 33 in the vicinity of the first objective lens 34. It is preferable not to arrange the components constituting the optical head on the inner circumference side of the optical disk. As shown in FIG. 3, the optical head base 5 has an arc-shaped recess so as to be accessible to the spindle motor 7, so that the optical head base 5 has a concave portion. If it is outside, a space for arranging the components constituting the optical head can be secured. Therefore, by utilizing the area outside the concave portion of the base 5, the first photodetector 36 and the first light source 31 that do not interfere with the spindle motor 7 are mutually connected with respect to the optical axis of the first collimating lens 33. Can be placed on the opposite side to V ヽ.

The optical head of this embodiment is intended to record / reproduce a large amount of information using an optical disk. In order to handle a large amount of information, it is necessary to increase the recording speed and reproduction speed of the information. In particular, when recording, it is necessary to change the intensity of the emitted light at a high speed to perform recording at a high speed. In other words, it is necessary to drive the first light source 31 and to modulate the current flowing to emit light at high speed. For this reason, it is preferable that a drive circuit for controlling a current for driving the first light source 31 or a large-scale integrated circuit (LSI) be arranged in the vicinity of the first light source 31. By arranging them close to each other, it is possible to prevent an increase in resistance due to a long wiring and a signal delay caused thereby.

The drive circuit that controls the drive current of the first light source 31 has many parts in common with the drive circuit that controls the drive current of the second light source 37a built in the integrated module 37. For this reason, the first light If the drive circuit of the light source 31 and the drive circuit of the second light source 37a are shared, and the first light source 31 and the second light source 37a are driven by a single drive circuit configured by LSI, the optical head can be reduced in size. It can be done.

As shown in FIG. 3, the optical head further includes a drive circuit 9 that drives the first light source 31 and the second light source 37a, and the drive circuit 9 includes the first light source 31 and the second light source. Preferably placed close to 37a. The first light source 31 and the second light source 37a and the drive circuit 9 are connected to the first collimator so that the optical head can be moved to the inner peripheral side of the optical disc and recording / reproduction can be performed on the inner peripheral side of the optical disc. The optical axis 33a of the lens 33 is preferably arranged on the outer peripheral side (arrow 33A) of the optical disc. As a result, the first light source 31 can be modulated at high speed, and the outer shape of the optical head can be reduced.

The optical head of the present embodiment is configured by two optical systems that use the first objective lens 34 and the second objective lens 41, respectively. Next, the arrangement of the two optical systems will be described.

As shown in FIGS. 2 and 3, the optical axes of the light beam 56 ′ ′ of the first light source 31 and the light beam 57 of the second light source 37a and the light beam 58 of the third light source 43a incident on the prism 60 are parallel to each other. Preferably it is. As a result, the slopes 60a and 60b of the prism 60 are both set perpendicular to the paper surface in FIG. 2, and the angles of incidence on the first objective lens 34 and the second objective lens 41 are set to the respective optical axes. And can be parallel. In addition, since both the inclined surfaces 60a and 60b can be set perpendicular to the paper surface, the rising prism 60 can be efficiently manufactured by cutting a bar that extends long in the vertical direction to the paper surface, for example. 60 manufacturing costs can be reduced.

[0097] As described above, when the two inclined surfaces 60a and 60b of the prism 60 are used for raising the light beam emitted from the light source, the inclined surfaces 60a and 60b are adjusted unlike the case of using two mirrors. Therefore, the optical axes cannot be adjusted independently of each other. For this reason, the first light source 31, the second light source 37a, and the third light source 43a are respectively connected to the base 5 (FIG. 3) with respect to the optical axes of the first light source 31, the second light source 37a, and the third light source 43a. It is preferable to provide a holder that can be slid in a perpendicular direction to adjust the position. By moving the first light source 31, the second light source 37a and the third light source 43a in the direction perpendicular to the respective optical axes, the optical axis angle of the light passing through the first collimator lens 33 and the second collimator lens 39 can be adjusted. adjust It is preferable.

As shown in FIGS. 1, 2, and 3, the first objective lens 34 and the second objective lens 41 are fixed to the movable body 45a of the objective lens actuator 45. The first objective lens 34 and the second objective lens 41 are preferably arranged substantially parallel to the Y direction, that is, the extending direction of the track groove of the first optical disc 35. When the first objective lens 34 and the second objective lens 41 are arranged in the T direction orthogonal to the Y direction, when the optical head accesses the outermost periphery and the innermost periphery of the optical disk, the objective lens that is not used becomes the spindle motor 7 ( May interfere with Fig. 1 and 2) and may interfere with the exterior of the equipment. By arranging the first objective lens 34 and the second objective lens 41 in the Y direction, the optical head can be prevented from interfering with the spindle motor and the exterior, and recording and reproduction can be performed correctly for any of the different types of optical heads. It becomes possible.

Further, as shown in FIG. 3, it is desirable that the second objective lens 41 is disposed on a straight line 7b extending approximately in the direction of movement of the optical head through the seek operation, passing through the center 7c of the optical disk. By arranging the second objective lens 41 in this way, for example, a diffraction grating is formed on a part of the member of the hologram 43b, a sub beam is formed, and tracking signal detection by the three beam method is performed using this. In particular, signal detection can be performed stably in the reproduction operation using the third light source 43a. At this time, since the first objective lens 35 is displaced from the line 7b, the tracking error signal can be detected by the one-beam method without using the sub beam in the recording / reproducing operation using the first light source 31. I want it.

[0100] Next, adjustment of the tilt of the first objective lens 34 and the second objective lens 41 in the movable body 45a will be described.

[0101] According to Patent Document 3, it is disclosed that two objective lenses can be integrally coupled. However, in general, when manufacturing an objective lens, coma aberration occurs due to manufacturing errors, which distort the convergent beam. This distortion is different for each objective lens. For this reason, it is preferable to reduce this coma aberration by tilting the two objective lenses at appropriate angles.

[0102] As shown in FIG. 1, first, after the first objective lens 34 is bonded to the movable body 45a, the inclination of the movable body 45a is adjusted, and the aberration of the convergent light by the first objective lens 34 is reduced. Then the second objective By adjusting the tilt of the lens 41 with respect to the movable body 45a, the aberration of the convergent light due to the second objective lens is reduced.

[0103] The procedure is as follows. First, when the light beam 56 ′ is converged by the first objective lens 34, the inclination of the entire movable body 45a is adjusted so that the coma aberration is minimized or the convergence spot is the most axially symmetric. . In this state, the inclination of the second objective lens 41 is adjusted with respect to the movable body 45a so that the coma aberration is minimized or the convergence spot is the most axially symmetric.

[0104] Force that may be considered to fix the second objective lens 41 to the movable body 45a first, and then to adjust the tilt of the first objective lens 34 relative to the movable body 45a. There is. The larger the NA, the smaller the distance between the lens surface and the optical disk surface, that is, the working distance (WD) force. Therefore, when adjusting the tilt of the first objective lens 34 with respect to the movable body 45a, it is necessary to insert a jig such as a pin set for changing the tilt of the first objective lens 34 even with a narrow spacing force. This is the force that makes it difficult to adjust the tilt.

In the optical head of the present embodiment, the shape of the second objective lens 41 is devised so as to be suitable for adjusting the tilt of the second objective lens 41 in the above-described procedure.

FIG. 6 schematically shows a cross-sectional shape of the second objective lens 41. The second objective lens 41 has a curved surface portion 41h for converging the light beam and a flat portion 41c around the curved surface portion 41h. Since the edge 41c is usually called “flange”, it is hereinafter referred to as the edge 41c.

[0107] In order to change the tilt of the second objective lens 41, it is necessary to insert a jig such as tweezers between the movable body 45a and the object lens. Tools such as tweezers should preferably not bend when changing tilt. When the jig was actually made and adjusted, it was found that if the jig thickness was 0.5 mm or more, the jig would not bend and adjustment would be easy. At that time, if the surface that condenses the light beam is scratched, the condensing performance of the objective lens deteriorates, so that only the edge 41c can contact the jig. Therefore, the width d of the edge 41c is preferably 0.5 mm or more. The movable body 45a must be lightweight because it needs to operate at a high speed with two objective lenses. From this point of view, the objective lens must also be small, and the edge 41c cannot be increased unnecessarily. The optical disk is the fastest and may rotate up to about 10,000 revolutions per minute. In order to realize an objective lens actuator that satisfies the above-mentioned performance, the edge 41c width is preferably lm m or less.

[0108] It is preferable to measure how much the objective lens is tilted after adjusting the tilt of the second objective lens 41. If the inclination is large as a result of measurement, the lens performance may be abnormal.In such a case, it may be better not to use the objective lens as a defective product. . The tilt of the lens can be measured by irradiating the edge 41c of the second object lens 41 with the light B1 and observing the reflection direction thereof as shown in FIG. In order to perform measurement correctly, it is necessary to obtain appropriate reflected light. For this reason, the upper surface 41g of the edge 4lc is preferably flat. Further, the upper surface 41g, which is the surface of the cono lc, is preferably mirror-finished so that the reflected light is not scattered. As a result of examination by the inventors of the present application, it was found that if the width of the upper surface is 0.2 mm or more, the reflected light is not scattered and the reflection direction can be measured accurately. From this point of view, the width d of the edge 41c needs to be 0.2 mm or more.

[0109] Normally, the outermost portion of the edge 41c has a curved surface portion of about 0.1 mm. Accordingly, the width d of the flat portion is preferably 0.3 mm (0.2 mm + 0.1 mm) or more.

[0110] Furthermore, when the second objective lens 41 is fixed to the movable body 45a, a hole for allowing light to enter the lens is provided. Only the edge 41c can do it. The error of the diameter of the objective lens is usually about ± 10 m, and the error of the diameter of the hole provided in the movable body 45a is usually ± 20 / ζ πι. Therefore, when these errors are added together, the result is ± 30 / ζ πι, and the maximum positioning of the second objective lens 41 and the movable body 45a is 60 μm.

[0111] The width of the edge 41c is preferably 60 m or more so that the edge 41c can come into contact with the movable body 45a even if an alignment error of 60 μm occurs. Normally, the outermost part of the edge 41c has a curved surface of about 0.1 mm. From this point of view, the width d of the edge 41c must be 0.16 mm (0.06 mm + 0.1 mm) or more. preferable.

[0112] From the above, if the width of the edge 41c is 0.16 mm or more and lmm or less, the inclination of the object lens after adjustment can be measured, so that defective products can be surely excluded. If it is 0.5mm or more and lmm or less, it is easier to adjust the tilt. It turned out to be preferable. By using the second objective lens 41 having an edge with a width in this range, it is easy to adjust the tilt of the objective lens by the method described above, and it is possible to adjust with high accuracy. Therefore, a high-performance optical head can be manufactured with high productivity.

As described above, according to the optical head of the present embodiment, since the various characteristic structures described above are adopted, it is compatible with a plurality of optical discs of different standards, has a small outer shape, and is stable and excellent. An optical head that exhibits optical characteristics is realized.

[0114] (Second Embodiment)

An embodiment of the optical information device according to the present invention will be described with reference to FIG.

The optical information device 104 includes an optical head 402, an electric circuit 403, and a motor 404.

[0116] The recording densities of the optical disks 407 to 409 are different from each other, and the operator selects one of the forces and places the selected optical disk on the turntable 405. The placed optical disk is fixed to the turntable 405 by a clamper 406 and is driven to rotate by a motor 404. Optical disks 407 to 409 correspond to the first optical disk 35, the second optical disk 320, and the third optical disk 46 of the first embodiment.

[0117] As the optical head 402, the optical head described in the first embodiment can be preferably used. The optical head can be moved in the tracking direction by a drive mechanism 401 such as a traverse motor, and can jump to a desired track.

The optical head 402 outputs a focus error signal and a tracking error signal to the electric circuit 403 in accordance with the positional relationship with the optical discs 407 to 409. In response to this signal, the electric circuit 403 sends a signal for finely moving the objective lens to the optical head 402. With this signal, the optical head 402 performs focus control and tracking control on the optical disks 407 to 409, and the optical head 104 reproduces information or records information.

[0119] According to the present embodiment, since the optical head of the first embodiment is provided, an optical information apparatus that can stably perform recording and reproduction operations of a plurality of optical disks having different recording densities is realized. be able to.

[0120] (Third embodiment)

With reference to FIG. 8, an embodiment of a computer according to the present invention will be described. [0121] The computer 105 includes the same optical information device 501 as the optical information device 104 described in the second embodiment. The computer 105 further uses an input device 503 such as a keyboard, a mouse, and a touch panel for inputting information, information input from the input device 503, information read from the optical information device 501 and the like. A computing unit 502 such as a central processing unit (CPU) that performs computation is provided.

[0122] Further, an output device 504 such as a cathode ray tube, a liquid crystal display device, or a printer that displays information such as a result calculated by the arithmetic device 502 is provided.

[0123] According to the computer 105, the optical information device 501 that is the same as the optical information device described in the second embodiment is provided. Or read out the information recorded on the optical disc, and process and edit the information.

[0124] (Fourth embodiment)

An embodiment of the optical disc player according to the present invention will be described with reference to FIG.

The optical disc player 106 includes the same optical information device 601 as the optical information device 104 described in the second embodiment. The optical disc player 106 further includes a conversion device 602 such as a decoder that converts an information signal obtained from the optical information device 601 into an image. The optical disk player 106 may also be used as a car navigation system. Further, a display device 603 such as a liquid crystal monitor may be further provided.

[0126] (Fifth embodiment)

An embodiment of an optical disk recorder according to the present invention will be described with reference to FIG.

The optical disc recorder 107 includes the same optical information device 701 as the optical information device 104 described in the second embodiment. In addition, a conversion device 702 such as an encoder that converts image information into information to be recorded on an optical disk by the optical information device 701 is further provided. A decoder 703 for converting an information signal obtained from the optical information device 701 into an image may be further provided. Further, an output device 704 such as a cathode ray tube for displaying information, a liquid crystal display device, or a printer may be provided.

[0128] (Sixth embodiment)

An embodiment of an optical disk server according to the present invention will be described with reference to FIG. The optical disk server 108 includes the same optical information device 801 as the optical information device 104 described in the second embodiment. Further, the server 108 captures information to be recorded in the optical information device 801 and outputs information read by the optical information device 801 to the outside, such as an input device 805 such as a keyboard, a mouse, and a touch panel for inputting information. Wired or wireless input / output terminal 802 is provided. As a result, it functions as an optical disk server that exchanges information with a network, that is, a plurality of devices such as computers, telephones, and TV tuners, and shares information with the plurality of devices. An output device 804 such as a cathode ray tube, a liquid crystal display device, or a printer that displays information may be further provided. Further, by providing a changer (not shown) for taking a plurality of optical disks into and out of the optical information device 801, a large amount of information can be recorded and accumulated.

[0130] Although the output device and the input device are shown in the second to sixth embodiments, only the input terminal and the output terminal are provided, and the output device and the input device are the second to sixth embodiments. The device of the form may not be provided.

Industrial applicability

The present invention is suitably used for an optical information apparatus such as an optical head and an optical disk apparatus that perform at least one of recording and reproduction with respect to various optical disks having different substrate thicknesses, corresponding wavelengths, recording densities, and the like. In particular, it is suitably used for an optical information device such as an optical disk device having a plurality of objective lenses.

[0132] Therefore, the present invention is suitably used for any system that stores information, such as a computer, an optical disc player, an optical disc recorder, a car navigation system, an editing system, a data server, and an AV component.

Claims

The scope of the claims

[1] a first light source that emits light of a first wavelength;

A beam splitter for branching the light emitted from the first light source into a first light beam and a second light beam respectively traveling in a second direction different from the first direction and the first direction;

A first collimating lens for converting the divergence of the first light beam;

A first mirror that changes a traveling direction of the first light flux whose divergence has been converted; a first objective lens that converges the first light flux whose traveling direction has changed toward a recording surface of a first optical disc;

A movable body holding the first objective lens;

A first photodetector for receiving the first light flux reflected on the recording surface of the first optical disc and converting it into an electrical signal;

A condensing lens for condensing the second light flux;

A second photodetector for receiving the second light beam collected by the condenser lens and converting it into an electrical signal;

With optical head.

[2] The beam splitter Taka is further provided with a second mirror for changing the traveling direction of the emitted second light beam,

2. The optical head according to claim 1, wherein the second mirror is disposed with respect to the beam splitter so as to change a traveling direction of a light beam traveling in the second direction in a direction orthogonal to the second direction.

[3] The optical axis of the second light flux whose traveling direction is changed by the second mirror and the optical axis of the first light flux whose traveling direction is changed by the first mirror are parallel to each other. 2. The optical head according to 2.

[4] The second photodetector has an outer shape having a longitudinal direction, and the second detector is disposed so that the longitudinal direction is substantially parallel to the optical axis of the first collimating lens. Item 4. The optical head according to Item 3.

[5] The optical head according to claim 4, wherein the second detector has an electrical connection terminal on a side surface located in the longitudinal direction.

[6] The apparatus further comprises a driving device for moving the position of the first collimating lens in a direction parallel to the optical axis of the first collimating lens,

6. The optical head according to claim 5, wherein the driving device is disposed on the outer peripheral side of the first optical disc with respect to the optical axis of the first collimating lens.

7. The optical head according to claim 6, further comprising a lens that includes a concave lens and a diffractive lens formed on a curved surface of the concave lens, and that corrects chromatic aberration of the first objective lens.

[8] The optical head according to [7], wherein the first light source and the first photodetector are arranged on opposite sides with respect to an optical axis of the first collimating lens.

[9] a second light source that emits light having a second wavelength longer than the first wavelength;

A second mirror that changes the traveling direction of the emitted light,

A second objective lens that converges the light of the second light source whose traveling direction has been changed by the second mirror toward the recording surface of the second optical disc;

9. The optical head according to claim 8, wherein the second objective lens is supported by the movable body.

10. The optical head according to claim 8, wherein the first light source and the second light source are arranged on the outer peripheral side of the first optical disc with respect to the optical axis of the first collimating lens.

[11] It further comprises a drive circuit for driving the first light source and the second light source,

10. The optical head according to claim 9, wherein the drive circuit is disposed in proximity to the first light source and the second light source.

12. The optical head according to claim 11, wherein the second wavelength is a wavelength used for DVD recording / reproduction, and the first wavelength is a wavelength used for recording / reproduction of an optical disc having a higher density than the DVD. ,.

13. The optical head according to claim 12, wherein the first objective lens and the second objective lens are arranged along a tangential direction of the first optical disc and the second optical disc.

14. The optical head according to claim 13, wherein the first objective lens is located on a straight line passing through a center of the first optical disc and parallel to a moving direction of the seek operation of the optical head.

15. The optical head according to claim 14, wherein the second objective lens has an edge having a width of 0.16 mm or more and 1 mm or less.

16. The optical head according to claim 15, wherein a surface of the edge of the objective lens is mirror-finished.

[17] An optical head as defined in claim 1,

A spindle motor for rotating the first optical disk;

An electric circuit for controlling the optical head based on a signal obtained from at least the first photodetector of the optical head;

An optical information device.

18. A computer comprising the optical information device as defined in claim 17.

19. An optical disc player comprising the optical information device as defined in claim 17.

20. An optical disc recorder comprising the optical information device defined in claim 17.

21. An optical disc server comprising the optical information device defined in claim 17.